[PATCH] blk-mq: fix a memory leak bug

From: Wenwen Wang
Date: Sun Jul 14 2019 - 03:03:41 EST

From: Wenwen Wang <wenwen@xxxxxxxxxx>

In blk_mq_init_allocated_queue(), a kernel buffer is allocated through
kcalloc_node() to hold hardware dispatch queues in the request queue 'q',
i.e., 'q->queue_hw_ctx'. Later on, if the blk-mq device has no scheduler
set, a scheduler will be initialized through elevator_init_mq(). If this
initialization fails, blk_mq_init_allocated_queue() needs to be terminated
with an error code returned to indicate this failure. However, the
allocated buffer is not freed on this execution path, leading to a memory
leak bug. Moreover, the required cleanup work is also missed on this path.

To fix the above issues, free the allocated buffer and invoke the cleanup

Signed-off-by: Wenwen Wang <wenwen@xxxxxxxxxx>
block/blk-mq.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e5ef40c..04fe077 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2845,6 +2845,8 @@ static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
struct request_queue *q)
+ int ret = -ENOMEM;
/* mark the queue as mq asap */
q->mq_ops = set->ops;

@@ -2906,11 +2908,9 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,

if (!(set->flags & BLK_MQ_F_NO_SCHED)) {
- int ret;
ret = elevator_init_mq(q);
if (ret)
- return ERR_PTR(ret);
+ goto err_hctxs;

return q;
@@ -2924,7 +2924,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
q->poll_cb = NULL;
q->mq_ops = NULL;
- return ERR_PTR(-ENOMEM);
+ return ERR_PTR(ret);